1. Field of the Invention
The present invention relates to image processing for executing processes according to the attributes of image regions.
2. Description of the Related Art
A color copying machine segments a scan image into regions, and appends region information indicating a text region or picture region to each segmented region. By switching the image processes of respective regions in accordance with the region information, suited image processes are respectively applied to the text region and picture region, thus obtaining a satisfactory print image.
A color printer renders and prints an image in accordance with print data which is input from a computer and is described in a language such as the page description language (PDL). In this case, since attributes (text, graphics, picture, and the like) of rendering objects are designated in the print data, the printer can obtain region information for each rendering object without region segmentation unlike in the color copying machine. The color printer appends region information for respective images obtained by rendering the rendering objects, and switches image processes in accordance with the region information to apply suited image processes to the text region and picture region, thus obtaining a satisfactory print image.
FIG. 1 is a block diagram showing the arrangement of a multi-functional peripheral equipment (MFP).
A printer driver, which runs on a computer 101, converts print instructions of application software (AP), which also runs on the computer 101, into print data, which is received by an MFP 102 via a network 100. The print data includes objects such as text, graphics, picture image, and the like.
A processor 108 as a controller of the MFP 102 stores the print data, which is received via a network interface card (NIC) 105, in a memory 107 via a crossbar switch 106. The processor 108 converts the print data stored in the memory 107 into a display list. The display list holds information such as text, graphics, and picture image, print of which is instructed by the AP of the computer 101.
A rendering processor 109 reads out the display list from the memory 107, and generates a print image by rendering objects according to the display list. Upon rendering the print image, the rendering processor 109 sets region information indicating text and picture based on the attributes of objects used to render respective images which form a print image, and appends the region information for each pixel.
Upon completion of rendering or when a print image storage area of the memory 107 is full of data, the processor 108 reads out the print image (or its some data) from the memory 107. The processor 108 spools the readout data on a hard disk drive (HDD) 111 via the crossbar switch 106 and a serial ATA interface (SATA I/F) 110. After that, the processor 108 reads out the spooled print image from the HDD 111, and transfers the readout image to the memory 107 via the SATA I/F 110 and crossbar switch 106 again, thus starting printing.
A printer 104 starts in response to an instruction from the processor 108, and feeds a paper sheet. After that, the print image is input to the printer 104 via the memory 107, the crossbar switch 106, an image processor 112 for the printer, and a printer I/F 113, and is printed. When the print image has the RGB data format, the image processor 112 converts the RGB data format into the CMYK data format. At the same time, the image processor 112 executes image processes such as gamut mapping (e.g., from sRGB to device CMYK), under color removal (UCR), masking, gamma correction, and the like according to the characteristics of the printer 104. These processes implement image processes suited to respective regions by switching color conversion tables in accordance with the region information appended to each pixel of the print image.
Upon reception of a copy instruction, the MFP 102 inputs a scan image scanned by a scanner 103 to an image processor 115 for the scanner via a scanner I/F 114. The image processor 115 executes image processes such as gamut mapping (from device RGB to, e.g., sRGB), resolution conversion, region segmentation, and the like according to the characteristics of the scanner 103, and stores the scan image that has undergone the image processes in the memory 107 via the crossbar switch 106. Each pixel of the scan image that has undergone the image processes is appended with region information indicating a text region or picture region by the region segment processing.
Upon completion of storage of the scan image in the memory 107, or when a scan image storage area of the memory 107 is full of data, the processor 108 reads out the scan image from the memory 107. The processor 108 spools the readout image in the HDD 111 via the crossbar switch 106 and SATA I/F 110. After that, the processor 108 reads out the spooled scan image from the HDD 111, and transfers it to the memory 107 again via the SATA I/F 110 and crossbar switch 106, thus starting printing. The subsequent processes are the same as those upon printing print data received from the computer 101.
Note that the printer I/F 113 and scanner I/F 114 use, e.g., a serial bus such as USB (Universal Serial Bus), IEEE1394, or the like.
FIGS. 2A to 2C show the relationship among print data, a rendered print image, and region information.
The print data shown in FIG. 2A includes independent text and picture objects, and also includes position information and size information required upon rendering these objects. Furthermore, the print data includes layout information between the objects, which indicates which object is located at an upper or lower position. The rendering processor 109 renders these objects according to the description of the display list to generate the print image shown in FIG. 2B. Then, the rendering processor 109 appends region information corresponding to the attributes of objects to each pixel, as shown in FIG. 2C.
FIG. 3 is a view for explaining the data format of the print image, and shows the data configuration of one pixel. One pixel data has, e.g., 8-bit region information attr in addition to, e.g., 8-bit R, G, and B data.
FIG. 4 is a flowchart showing the processing executed when the image processor 112 converts pixel data in the RGB format into CMYK data.
The image processor 112 inputs pixel data in the RGB format (S1), and checks with reference to the region information attr included in the pixel data if that pixel belongs to a text region (S2). If the pixel belongs to the text region, the image processor 112 sets a conversion table for the text region (S3); otherwise, it sets a conversion table for a picture region (S4). The image processor 112 converts the pixel data in the RGB format into CMYK data using the set conversion table (S5). The image processor 112 repeats this processing to all pixel data of the print image.
However, when the AP of the computer 101 issues a print instruction of a raster image or issues that of a scan image of a scanner connected to the computer 101, print data including only objects of a picture attribute is input to the MFP 102. To this picture image, rasterized text may be pasted like the print image shown in, e.g., FIG. 2B. However, since the print data indicates a picture attribute, even if it includes text, a print image in which region information indicating a picture region is appended to pixels is generated. As a result, the print image is applied with the image processing suited to the picture region, and is printed. Therefore, the image quality of its text region deteriorates.